AkuLite Report 6, SP Report 2013:17 Förslag
The survey has been performed in occupied apartment buildings in nine different cities, from Umeå in the north to Varberg in the south of Sweden. Seven of the buildings have a lightweight wooden framework and one a lightweight steel framework. Yet another building with concrete framework was included in the survey as a reference.
In the used questionnaire the residents were asked if they experience springiness and vibrations annoying. The questions dealt with different excitation sources as vibrations induced by the residents themselves or someone else walking in the same room, neighbours that induce vibrations, slamming doors and traffic. Also different ways to perceive vibrations were inquired about, i.e. are the vibrations perceived by feeling, hearing or sight. The residents’ sensitivity to vibrations and if they have to adjust their way of walking not to disturb family members or neighbours were also asked about. The last question was about the satisfaction with the quality of floors and walls.
The questionnaire seems to work quite well in general. From the ratings it is not possible to say in what way the residents are most annoyed, by feeling the vibrations, hearing or seeing furniture or objects move. The vibrations appear to be perceived in several ways and it could be possible that the residents are not able to make difference between the perceived disturbances if they occur simultaneously. It may be concluded from the ratings that annoyance by vibrations is not a problem in buildings with concrete framework, but in buildings with lightweight framework the residents clearly are annoyed by vibrations.
The collection of objective data about vibration performance of floors were carried out by field measurements according to a common measurement protocol developed within the AkuLIte project. The physical objective parameters related to floor vibrations were the deflection d due to a point load at midspan, the fundamental frequency f1 of the floor and the total maximum acceleration Amax of the floor when excited with an impulse ball at the centre of the floor. A principal component analysis and a linear regression analysis were performed to find relationships between subjective ratings and objective data a principal component analysis and a linear regression analysis were performed.
From the correlations analysis it may be concluded that the deflection d due to a concentrated point load at midspan of the floor is the best of the investigated parameter for predicting vibration disturbance. All the floors in the investigation do fulfill the deflection requirement for timber floors in the Swedish building regulation, which is a maximum deflection of 1.5 mm when loaded with a 1 kN point load at midspan of the floor. If considering the regression line of residents ratings of general vibration disturbance and deflection d it is found that a deflection of 1.5 mm would result in 52 % of the residents being “somewhat annoyed, annoyed or very annoyed”. That is a rather high number and points to the fact that the limit should be sharpened. The result maybe not surprising as the methods and limits used today were developed at a time when timber joist floors were mostly used in single family housing. This investigation has involved apartment buildings and it is obvious that the tolerance is lower, even if it is not evident that the disturbance due to vibrations is induced by neighbours. To be able to propose any reliable new limits for the vibration criteria more data is needed, meaning that both measurements and surveys have to be carried out in more buildings. To have more reliable vibration values a common method for measurement and evaluation of fundamental frequency and acceleration levels have to be developed and included in the measurement protocol.
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